Process for the stabilization of chlorinated hydrocarbons



United States Patent "ice PROCESS FOR THE STABILIZATION OF CHLORINATED HYDROCARBONS Nestor Daras, Ixelles-Brussels, and Andre Ryckaert, Uccle-Brussels, Belgium, assignors to Solvay & Cie, Brussels, Belgium, 9. company of Belgium No Drawing. Filed Sept. 4, 1959, Ser. No. 838,047

Claims priority, application Belgium Sept. 10, 1958 12 Claims. (Cl. 260-6525) The present invention concerns a process for stabilizing chlorinated hydrocarbons, particularly perchlorethylene, with a view to avoiding decomposition of these products and the simultaneous formation of acid during storage or when being used.

' It is known that under the action of heat and oxygen, chlorinated hydrocarbons undergo an oxidation which is catalyzed by different agents such as light and certain metal salts such as salts of aluminum, iron and magneslum.

In order to slow down this oxidation it has been proposed to add to these chlorinated hydrocarbons small quantities of various products such as alcohols, organic and mineral basic products, phenols, epoxy compounds, etc.

Whatever the eflectiveness of these stabilizers may be as regards avoiding oxidation of chlorinated hydrocarbons, they are generally incapable of preventing decomposition of said chlorinated hydrocarbons in the course of their use. 0'

In fact, addition of a single stabilizing compound is generally insufficient to avoid degradation of chlorinated hydrocarbons. On the other hand, the addition of several stabilizing compounds does not always give the expected result, either. because of their incompatibility or because too large a quantity of products is necessary to ensure good stabilization.

- The present invention concerns a new combination of reagents for stabilizing chlorinated hydrocarbons, such combination giving surprising results.

According to the invention, chlorinated hydrocarbons and particularly perchlorethylene, are stabilized by adding thereto small quantities of a primary pentanol or a mixture of primary pentanols and of a nitrogen base chosen from the group comprising pyridine, a-picoline (Z-methylpyridine) and morpholine (tetrahydro-l,4-oxazine). u-Picoline is preferably used. Among the primary pentanols there may be cited: primary n-amyl alcohol, primary isoamyl alcohol (3-methyl-2-butanol), and primary active amyl alcohol (2 methyl-l-butanol). An example of a mixture of primary pentanols is fermentation amyl alcohol which contains essentially primary isoamyl alcohol and primary active amyl alcohol.

The applicants have found that alcohols, as well as nitrogen bases even if used in large quantities, could not in themselves ensure stabilization of chlorinated hydrocarbons, but that the combinatiton of these compounds led to a pronounced and unexpected synergistic eifect.

The stabilizing action of the compounds used for improving the resistance of chlorinated hydrocarbon to decomposition is shown by the following laboratory test:

200 cm. of perchlorethylene, to which the specified stabilizers were added, are placed in a 500 cm. Erlenmeyer flask fitted with an upright water-fed cooler.

Oxygen is bubbled through the perchlorethylene by means of a thin tube of 3 mm. inside diameter, extending into the flask to within 6 mm. of the bottom. A steel test-bar is suspended from said tube, at the base of the 2,966,524 Patented Dec. 27, 1960 cooler; another, smaller, is placed at the bottom of the flask.

The flow of oxygen is regulated to from 10 to 12 bubbles per minute, by means of a tube extending into a water valve. apparatus.

The perchlorethylene is heated to boiling and kept boiling with reflux for 48 hours by means of a w. frosted glass incandescent lamp, fixed in a stainless steel cylinder of mm. height and 100 mm. inside diameter. The steel wall of said cylinder is 1 mm. thick. On the top of this cylinder there is mounted a ring of 132 mm. outside diameter, 82 mm. inside diameter and 2 mm. thickness. The bottom of the flask, resting on this ring is thus 30 mm. from the lamp. Four diametrically opposed openings, 40 mm. high and 20 mm. wide, are provided This bubbler is placed upstream of the test in the lower part of the cylinder in order to ensure suitable ventilation of the apparatus. 7

The power of the lamp not being suflicient tor ensuring regular boiling of the perchlorethylene, the apparatus should be heat insulated. To this eifect, the Erlenmeyer flask is surrounded by a covering constituted by a glass cylinder, of 121 mm. inside diameter, 147 mm. height and 3 mm. thickness, lined inside and outside with asbestos paper and filled with glass wool. The assembly is covered with a square piece of asbestos-board provided with a central hole for the neck of the flask. This heat insulation reduces the losses of heat to a minimum, thus enabling regular boiling of the perchlorethylene and improving reproduction of the results.

At the end of the test, 50 cm. samples are stirred with 100 cm. of water for 3 minutes. The acidity of the extract is titrated with NaOH in the presence of bromocresol green. The results are expressed in percent by weight of hydrochloric acid and make it possible to compare the efliciency of the stabilizers used.

The table below shows the influence of alcohols (including the primary pentanols) and/ornitrogen bases on the stability of perchlorethylene.

Acidity in Percent by Test No. Stabilizer ing/l. weight of HCl formed 0. 0640 500 0. 0068 500 0.0280 500 0.0220 500 0. 0126 6 a-PiCOlil'lO 100 0. 0140 7. Mornhnlinp 100 0.0261 8 Pyridine 100 0.0288

{Noirmal amyl almhnl 500 9 a-picoline 100 0. 0005 Normal amyl alcohol 500 l0 morpholine 100 0. 0044 11 {Normal amyl alcohol 500 pyridine 0.0066 Tertiary amyl alcohol. 12

a-picoline Tertiary amyl alcohol l3 morpholine 0. 0510 Tertiary amyl '11 ool'lnl 50 14 pyridine 100 0. 0440 15 {Fermentation amyl alcohol 500 a-picoline 100 0.0022 {Isobutyl alcoh 500 16 a-picoline 100 0. 0153 lsobutyl alcohol 500 17 morphollne I 100 0. 0490 Isobutyl alcohol 500 18 pyridine 100 0. 0090 The results show that alcohols (including primary pentanols) and nitrogen bases, even in large quantities, cannot alone ensure stabilization of chlorinated hydrocarbons.

On the contrary, the combination of primary pentanols and nitrogen bases produces a considerable synergistic effect, particularly in the case of the combination which contains tat-picoline.

The quantity of stabilizing material to be used in the process according to the present invention may generally be from 0.1 to g. of primary pentanol and from 0.05 to 0.5 g. of nitrogen bases, per liter of chlorinated hydrocarbon to be stabilized. Preferably there will be used 0.3 to 2 g. of pentanol and 0.1 to 0.2 g. of nitrogen base per liter of chlorinated hydrocarbon.

According to the present invention it has also been found that it is possible to improve occasionally the stabilizing action of the combinations described, by adding quantities comprised between 0.005 and 0.02 g. of a phenol, such as phenol, cresol, thyrnol, etc. per liter of chlorinated hydrocarbon.

While the compositions described above show themselves to be particularly efficient in the stabilization of perchlorethylene, they can also be used for the stabilization of other chlorinated solvents such as trichlorethylene, carbon tetrachloride, dichlorethane, trichlorethane, etc.

We claim:

1. A process for the stabilization of a chloroethylene which comprises incorporating in said chloroethylene per liter thereof 0.1 to 10 grams of a primary pentanol and 0.05 to 0.5 gram of a nitrogen base selected from the group consisting of morpholine, pyridine, and picoline.

2. A process for the stabilization of a chloroethylene which comprises incorporating in said chloroethylene per liter thereof 0.1 to 10 grams of a primary pentanol selected from the group consisting of normal amyl alcohol, primary active amyl alcohol, and primary isoamyl alcohol, and 0.05 to 0.5 gram of a nitrogen base selected from the group consisting of morpholine, pyridine, and picoline.

3. A process for the stabilization of a chloroethylene which comprises incorporating in said chloroethylene per liter thereof 0.1 to 10 grams of a primary pentanol and 0.05 to 0.5 gram of picoline.

4. A process for the stabilization of a chloroethylene which comprises incorporating in said chloroethylene per liter thereof 0.1 to 10 grams of normal amyl alcohol and 0.05 to 0.5 gram of picoline.

5. A process for the stabilization of a chloroethylene which comprises incorporating in said chloroethylene per liter thereof 0.1 to 10 grams of a primary pentanol and 0.05 to 0.5 gram of a nitrogen base selected from the group consisting of morpholine, pyridine, and picoline, and 0.005 to 0.02 gram of phenol.

6. A process for the stabilization of a perchloroethylene which comprises incorporating in said perchloroethylene per liter thereof 0.1 to 10 grams of a primary pentanol and 0.05 to 0.5 gram of a nitrogen base selected from the group consisting of morpholine, pyridine, and picoline.

7. A stabilized composition comprising a chloroethylene normally subject to degradation and per liter thereof 0.1 to 10 grams of a primary pentanol and 0.05 to 0.5 gram of a nitrogen base selected from the group consisting of morpholine, pyridine, and picoline.

8. A stabilized composition comprising a chloroethylene normally subject to degradation and per liter thereof 0.1 to 10 grams of a primary pentanol selected from the group consisting of normal amyl alcohol, primary isoamyl alcohol, and 0.05 to 0.5 gram of a nitrogen base selected from the group consisting of morpholine, pyridine, and picoline.

9. A stabilized composition comprising a chloroethylene normally subject to degradation and per liter thereof 0.1 to 10 grams of a primary pentanol and 0.05 to 0.5 gram of picoline.

10. A stabilized composition comprising a chloroethylene normally subject to degradation and per liter thereof 0.1 to 10 grams of normal amyl alcohol and 0.05 to 0.5 gram of picoline.

11. A stabilized composition comprising a chloroethylene normally subject to degradation and per liter thereof 0.1 to 10 grams of a primary pentanol and 0.05 to 0.5 gram of a nitrogen base selected from the group consisting of morpholine, pyridine, and picoline and 0.005 to 0.02 gram of phenol.

12. A stabilized composition comprising a chloroethylene normally subject to degradation and per liter thereof 0.1 to 10 grams of a primary pentanol and 0.05 to 0.5 gram of a nitrogen base selected from the group consisting of morpholine, pyridine, and picoline.

References Cited in the file of this patent UNITED STATESPATENTS 2,338,297 Mugdon et al Jan. 4, 1944 2,371,644 Petering et 'al. Mar. 20, 1945 FOREIGN PATENTS 493,875 Great Britain Oct. 17, 1938 551,584 Great Britain Mar. 2, 1943 

1. A PROCESS FOR THE STABILIZATION OF A CHLOROETHYLENE WHICH COMPRISES INCORPORATING IN SAID CHLOROETHYLENE PER LITTER THEREOF 0.1 TO 10 GRAMS OF A PRIMARY PENTANOL AND 0.05 GRAM OF A NITROGENJ BASE SELECTED FROM THE GROUP CONSISTING OF MORPHOLINE, PYRIDINE, AND PICOLINE. 